1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a semiconductor device suitable for use in a camera system (camera unit) constitution.
2. Description of Related Art
In recent years, electronic devices such as portable telephones and personal computers have come to be installed with a camera system (camera unit) comprising a CCD image sensor, CMOS image sensor, or similar.
Such camera systems are mainly constituted by a camera portion, an image processing device (for example a DSP (Digital Signal Processor) or the like) for processing image signals (signal charges) generated by the camera portion in response to incident light on the camera portion, and a display device or the like for displaying an image corresponding to the image signals processed by the image processing device.
The camera portion is mainly constituted by a semiconductor device for capturing images (also to be referred to simply as “image-capturing semiconductor device” hereinafter) comprising a light-receiving element portion which is mounted on a printed circuit board (mother board), and a lens. In the camera portion, condensed light from the lens which enters the light-receiving element portion in the image-capturing semiconductor device is converted into a signal charge, whereupon this signal charge is outputted to the image processing device.
Conventionally, such image-capturing semiconductor devices are mounted on a printed circuit board via thin metal wires (a wire bonding method).
When such a wire bonding method is used, however, inductance in the bonding parts rises, making impedance matching between the circuits in the image-capturing semiconductor device difficult.
Moreover, the wire loop causes the volume required by the image-capturing semiconductor device to increase. The region occupied by the image-capturing semiconductor device itself is also large, and hence many problems need to be solved.
Thus in recent years research into wireless bonding methods in which the image-capturing semiconductor device and the printed circuit board are connected by external terminals such as solder balls has been flourishing.
Currently, WCSP (Wafer-level Chip Size Package) is being proposed as a constitution employing a wireless bonding method (see, for example, KOHYO Publication No. 2002-512436)
A WCSP is a CSP which is packaged at substantially identical outer dimensions to the outer dimensions of the semiconductor chip, and particularly one which is separated into individual packages following the completion of an external terminal forming step when in wafer form in order to reduce manufacturing costs.
An advantage of this WCSP is that the external terminals which are electrically connected to the semiconductor chip can be redisposed in a desired position by means of a rewiring layer, and thus wiring design freedom is increased. Moreover, signal attenuation can be suppressed in comparison with a WB system, and matching of the characteristic impedance of the signal line with the impedance of the semiconductor chip can be easily achieved, providing an excellent high frequency characteristic.
In accordance with the recent trend toward electronic device miniaturization, the development of high density packaging technologies for semiconductor devices is advancing.
In order to realize such high density packaging, an MCP (Multi Chip Package) in which a plurality of chips is disposed two-dimensionally in one package or stacked in the direction of thickness of the semiconductor chips has been proposed.
In conventional image-capturing semiconductor devices employing a WCSP constitution (see KOHYO Publication No. 2002-512436), however, the rewiring layer which electrically connects the semiconductor chip and external terminals is bent in a complex fashion to form a reversed “c”.
As a result, the device constitution itself and the manufacturing process thereof become complicated, and there has been concern about consequent rises in the cost of semiconductor devices.
It is therefore an object of this invention to provide a semiconductor device having a constitution which is simplified in comparison with a conventional device and which can be constructed using fewer processes than a conventional device on the basis of a WCSP constitution and manufacturing process, the scope of application of which is expected to increase in the future due to the significance thereof, and also to provide a camera system having smaller dimensions than a conventional camera system.